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Wi-Fi on a Boat
Making shore-based Wi-Fi Internet work well on a boat. __FORCETOC__ Common Problems In locations where shore-based Wi-Fi signals are strong, using them for Internet access on a boat is comparable to using Wi-Fi hotspots on land. However, the marine environment tends to exacerbate general Wi-Fi problems and create other problems of its own: * Boat hulls and sailboat masts can block radio signals, reducing range. * Movement of other boats can cause interruptions of Wi-Fi connections. * Location of a Wi-Fi antenna in a cabin below deck can further reduce range. * It may be difficult to get close enough to the Wi-Fi access point for sufficient signal, especially when anchored. * Boat movement can result in aiming problems with highly directional antennas (even when tied up). * Moisture in the marine environment can result in electronic failures. Improving Wi-Fi Higher Power While it may seem that higher power Wi-Fi might help to improve your range, that's not necessarily true, since higher power only helps on transmit, not receive. Thus it's only likely to help if the other end of your connection is using higher power as well, which is often not the case. In other words, what you may well wind up with is an alligator, big mouth but small ears. Also, unnecessarily high transmit power will tend to increase your interference with other Wi-Fi users, making you a bad neighbor. It's usually much better to just improve your antenna, which helps both transmit and receive. Better Antenna Usually the best way to improve range is to use a better antenna (or reflector with a standard antenna), which helps both transmit and receive. Better antennas work by being directional: * concentrating radio energy/sensitivity to/from the desired direction instead of wasting it in other directions, and * reducing interference from other radio sources not in the desired direction (path). The improvement in antenna performance is referred to as gain, where a higher number indicates the amount of performance improvement expressed in dBi. It takes an increase of 3 dBi to double range; e.g., as compared to a typical 2 dBi antenna: * 5 dBi antenna has double the range * 8 dBi antenna has 4 times the range However, a highly directional antenna can be problematic on a boat, since it must be kept aimed accurately at the remote end of the connection, which can be difficult on a boat floating in the water (even when tied up). The width (angle) of the directional pattern (both vertically and horizontally) can be used to see how accurately the antenna must be aimed. The simplest and easiest improvement is to use a higher-gain omnidirectional antenna (6-12 dBi), thereby avoiding the need to aim the antenna. Such an antenna works by concentrating energy/sensitivity in the horizontal direction that would otherwise be wasted vertically (up or down). Antenna Location Higher antenna locations tend to have less interference (e.g., from other boats) than lower locations, so in general it's a good idea to locate the antenna as high as is practical. On a sailboat, the ideal location is at the top of the mast. Since signal loss in the cable between the radio unit and the antenna increases rapidly with the length of the cable, it's better to locate the radio unit next to the antenna, and use lossless cable to support the radio unit, either USB or Ethernet, both of which have advantages and disadvantages (as noted below). Temporary Setup Setup as needed, and packed away when not in use. Ideally the radio unit and antenna are as high as possible (e.g., up on the top of the cabin), usually connected by cable: USB Advantages: * Simplicity * Lower cost Typical USB setups: * Hawking HWU54D Hi-Gain USB Wireless-G Adapter (6 dBi, aiming less critical) * Hawking HWU8DD Hi-Gain USB Wireless-G Dish Adapter (8 dBi, aiming more critical) Maximum length of a USB cable is 5 meters (about 16 feet), although that distance can be multiplied by means of one or more USB active extension cable(s), effectively a standard USB cable married to a one-port USB hub (e.g., StarTech USB 2.0 Active Extension Cable USB2FAAEXT15). Note: USB Internet connection can be shared by means of Internet Connection Sharing and a separate network (e.g., Ethernet). Ethernet Advantages: * Long cable (up to 100 meters) * No USB driver needed * Support multiple clients with a hub or switch Typical Ethernet setup: * Buffalo Wireless-G High Power Ethernet Converter WLI-TX4-G54HP * Buffalo 6 dBi Detachable High Gain Directional Antenna WLE-AT-DACB (if needed, must be properly aimed) Power can be provided by means of a power cable, or it may be possible to provide power by means of Power over Ethernet. Check manufacturer specs. Permanent Installation thumb|SENAO Outdoor Wireless Multi-Client Bridge/Access Point/WDS SOC-3220 This will give far more range than regular Wi-Fi at deck or cabin level: *Install weatherized high-gain omnidirectional antenna as high as is practical (if on a sailboat, ideally at top of mast) *Install weatherized Ethernet client bridge (e.g., ''SENAO SL-2611CB5 or SOC-3220) as close to antenna as possible (as in outdoor access point picture above, in order to minimize signal loss in antenna cable) *Run weatherized CAT5 cable from Ethernet client bridge (if on a sailboat, down/inside mast) *Power client bridge with Power over Ethernet *At cabin end of Ethernet cable, put: ** Hub or switch (for wired network connections) ** Wi-Fi access point (for Wi-Fi network connections) ** Bluetooth access point (''e.g., ''ANYCOM AP-2002) (for Bluetooth network connections) Wired versus Wireless Clients +-------------+ +-------------+ |Shore Wi-Fi | |Shore Wi-Fi | |Access Point | |Access Point | +------.------+ +------.------+ . . . . .wireless .wireless . . . . +------.------+ +------.------+ |Boat Ethernet| |Boat Ethernet| |Converter | |Converter | +------+------+ +------+------+ |Ethernet cable |Ethernet cable | +------+------+ | |Boat Wi-Fi | | |Access Point | | +------.------+ | . | .wireless | . +------+------+ +------.------+ | Computer | | Computer | | | | | +-------------+ +-------------+ ''Note: In order to minimize possible interference, a boat Wi-Fi access point should ideally be on a different minimally-overlapping channel (1, 6, 11 in the USA) than the shore access point. Managing the Wireless Ethernet Bridge When using a wireless Ethernet client bridge, IP addresses of networked clients on the boat (wired or wireless) are normally assigned by a shore-based DHCP server. The problem is that the wireless Ethernet client bridge will typically have a fixed IP address for management that won't necessarily be on the same subnet as IP addresses set by shore-based DHCP servers, preventing networked clients from directly managing the wireless Ethernet client bridge. Two possible solutions to this problem: # Use two network adapters {wired or wireless) on a given networked client: ## One configured by (shore-based) DHCP for Internet access ## The other configured manually just for managing the wireless Ethernet client bridge # Use a multi-homed Ethernet adapter with both a static address and a DHCP address Power Many standalone low-end networking devices that use separate "wall wart" type power supplies are able to tolerate a relatively wide range of input voltage, and can be run directly from 12 VDC boat power with an appropriate adapter cable. Check manufacturer input voltage specs if possible. Relaying and Mesh Networks When some boats are too distant from a shore access point for a direct Wi-Fi connection, it may be possible to setup nearer boats to repeat or relay the Wi-Fi signal to more distant boats in a Wireless Distribution System. International Use Wi-Fi channels are standardized, but vary slightly in different parts of the world. Many Wi-Fi devices will work properly anywhere in the world, either by means of a configuration option (preferable), or by means of different firmware loads (clumsy). See Wi-Fi Channels. Many Wi-Fi devices are able to operate properly anywhere in the world, either by means of a configuration option (preferred), or by means of different firmware loads (clumsy). External Links * Wi-Fi Internet solutions for boaters and marinas * MarineNet Wireless ** WiFi Antenna Installations * Mini-Box.com